1. Field of the Invention
The present invention relates to a curtain airbag which is inflated and deployed along a side surface portion in an occupant compartment of a vehicle to protect an occupant in the event of a vehicle side impact crash or rollover (overturn).
2. Description of the Related Technology
In recent years, high levels of safety performance have been required of vehicles, and this tendency is common to countries around the world. At present, in each country in the world, vehicles are mostly standard-equipped with airbags as vehicle safety devices. Business companies involved in the development of vehicles have taken up “a further safety improvement” as an important theme in their development and, following this theme, new airbags are continually being developed.
Standards for evaluating vehicle safety differ from country to country, and each business company performs development such that its products can meet evaluation standards in many countries. For example, in the United States, which has the largest number of automobiles in the world, FMVSS (Federal Motor Vehicle Safety Standards) are issued by the NHTSA (National Highway Traffic Safety Administration). At present, in a Notice for Proposed Rulemaking (NPRM) for FMVSS planned to be issued by the NHTSA in future, the requirement of “reducing the probability of occupant ejection from a vehicle through a side window using an ejection mitigation system in the event of a side impact crash or rollover (overturn)” is proposed (FMVSS 226). The requirement can be met by providing a curtain airbag as a device intended to reduce ejection from a vehicle, which forms the ejection mitigation system.
A curtain airbag is an airbag disposed above a door so as to be inflated and deployed along vehicle side windows, upon the occurrence of an impact, to protect an occupant. When inflated and deployed, a typical curtain airbag is designed to have a pressure duration longer than that of a front airbag or the like. This is longer duration is needed because, if a rollover occurs subsequently to a side impact crash, the time during which an impact may occur is long. Thus, the curtain airbag is intended to restrain an occupant by retaining the inflated state thereof during the time of a rollover and prevent ejection from a vehicle.
To ensure the successful prevention of occupant ejection from a vehicle described above, the curtain airbag needs to be inflated and deployed while covering each of a plurality of side windows present in a side surface portion of the vehicle. For example, the curtain airbag described in Japanese Patent Application Laid-Open No. 2007-237864 is disposed in a 3-row-seat vehicle, and capable of covering even a fixed-type side window (so-called quarter window) lateral to a third-row seat.
However, to inflate a large-capacity airbag which covers even a portion lateral to a third-row seat such as the curtain airbag described in Japanese Patent Application Laid-Open No. 2007-237864, a high-output gas generator (inflator) is needed. In general, as represented by the third-row seat and the quarter window that are described above, a side window lateral to a rearmost seat mostly has a shape different from those of the other side windows forward thereof and an area smaller than those thereof. If an inflation region is excessively expanded so as to reach such a side window, the output of the inflator may need to be increased, resulting in increased manufacturing costs.